The present invention relates to a metal ion source, and more particularly to an ion source capable of producing a stable ion beam for an extended period of time.
A known metal ion source for generating a beam of gallium ions includes a curved tungsten filament and an emitter spot-welded to the tungsten filament. A mass of gallium, for example, is held by the curved tungsten filament for flowing down the emitter toward its pointed end for field evaporation and ionization. The amount of gallium which can flow and be ionized varies with the amount thereof held by the filament, with the result that the ion source cannot produce a stable ion beam for an extended period of time.